JP2011095624A - Image forming apparatus and method for cleaning image carrier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus efficiently cleaning an image carrier for carrying a developer using a cleaning sheet. <P>SOLUTION: This image forming apparatus includes a conveying means that conveys a sheet to the image carrier 28 for carrying the developer and includes a nipping conveying means 6 capable of conveying the sheet while nipping it by rotation driving, and a controlling means for controlling the conveying means. When a tip 50A of the cleaning sheet is conveyed to a counter position 50C with at least the image carrier by the conveying means, the controlling means stops the driving of the conveying means, executes the cleaning operation of driving the image carrier 28K in a state nipped by the nipping conveying means 6, then conveys the cleaning sheet 50 by a predetermined distance Lm shorter than the distance Lr from the part 50F nipped by the nipping conveying means 6 to the rear end 50B, and executes the cleaning operation again. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to a method for cleaning an image carrier of an image forming apparatus using a cleaning sheet.

  Conventionally, as a method for cleaning an image carrier of an image forming apparatus, for example, Patent Document 1 discloses that a circumferential speed of a registration roller or a fixing roller is different from a circumferential speed of a photosensitive drum (image carrier) or cleaning. A technique is disclosed in which a cleaning sheet is rubbed against a photosensitive drum by hooking a conveyance restraining member provided on the sheet to a sheet feeding port to clean the photosensitive drum.

JP 09-185302 A

  However, in the above-described prior art documents, when cleaning is performed using a registration roller or a fixing roller so as to provide a speed difference, the cleaning sheet is not in a fixed state and is transported by a photosensitive drum, which may not necessarily be efficiently cleaned. was there.

  In addition, when the cleaning sheet is fixed by hooking the conveyance restraining member on the paper feed port, cleaning is continued at a part of the fixing portion of the cleaning sheet, the cleaning performance is deteriorated, and the cleaning cannot be performed efficiently. There was a fear.

  The present invention provides a technique for efficiently cleaning an image carrier carrying a developer by using a cleaning sheet.

  As means for achieving the above object, an image forming apparatus according to a first aspect of the present invention is an image carrier that carries a developer and a conveying means that conveys a sheet to the image carrier. A conveyance unit including a conveyance unit that can convey the sheet while nipping the sheet; an image forming mode in which the developer image on the image carrier is transferred onto the sheet; and a attachment on the image carrier by a cleaning sheet. A switching unit that switches between a cleaning mode for removing a kimono, and a tip of the cleaning sheet conveyed by the conveying unit to at least a position facing the image carrier in the cleaning mode; The driving is stopped and the image carrier is driven in a state where the cleaning sheet is held by the holding and conveying means. Run the Ningu operation, Thereafter, the drive of the conveying means and said image bearing member, perform the conveying operation for conveying the cleaning sheet by a predetermined distance, and control means for executing the cleaning operation again.

  According to this configuration, for example, the image carrier is cleaned by the cleaning sheet in a state where the cleaning sheet is nipped by a nipping and conveying unit such as a registration roller. Further, the cleaning sheet is moved by a predetermined distance that can be re-cleaned, and the image carrier is cleaned again at another portion of the cleaning sheet. Therefore, the image carrier can be efficiently cleaned using the cleaning sheet effectively. Here, the “tip portion of the cleaning sheet” does not mean the most advanced portion of the cleaning sheet, but means the vicinity of the most advanced portion of the cleaning sheet including at least the most advanced portion. The same applies to the rear end portion of the cleaning sheet.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect of the present invention, a plurality of the image carriers are provided to support the developer of each color, and the conveying means faces each of the image carriers, and the sheet The predetermined distance is a transport distance that is not an integral multiple of the distance between the contact portions between two image carriers adjacent to each other and the cleaning sheet, and the control When the leading end portion of the cleaning sheet is transported to a position facing the image carrier at the most downstream side in the transport direction, after performing the cleaning operation on each image carrier, the transport operation is performed for the transport distance. And the cleaning operation for each image carrier is executed again.

  According to this configuration, when performing the cleaning operation again, it is possible to avoid the cleaning of the other image carrier at the cleaned portion, and the cleaning can be performed efficiently. In addition, since the leading end portion of the cleaning sheet is conveyed to a position facing the image carrier at the most downstream side in the conveyance direction, it is possible to suppress wear due to direct friction between the image carrier and the conveyance unit.

  According to a third aspect of the present invention, in the image forming apparatus of the first aspect, the image carrier is provided in a plurality to carry the developer of each color, and the conveying means faces the image carrier, and the sheet The predetermined distance is a transport distance that is not an integral multiple of the distance between the contact portions between two image carriers adjacent to each other and the cleaning sheet, and the control means When the leading end portion of the cleaning sheet is conveyed to at least a position facing the most upstream image carrier to be cleaned in the conveyance direction of the plurality of image carriers, the most upstream image carrier The cleaning operation for the uppermost image carrier is performed again after the cleaning operation for the uppermost-stream image carrier.

  The deposits on the image carrier other than the developer, such as paper dust, have a high probability of adhering to the most upstream image carrier. Therefore, according to this configuration, it is possible to efficiently remove deposits on the image carrier by cleaning only the most upstream image carrier without cleaning all the image carriers. In addition, since only the most upstream image carrier needs to be cleaned, the cleaning sheet can be shortened.

According to a fourth aspect of the present invention, in the image forming apparatus according to the second or third aspect of the invention, the transport distance is shorter than a distance between contact portions between the two image carriers adjacent to each other and the cleaning sheet. .
According to this configuration, since the moving amount of the cleaning sheet when performing the cleaning operation again can be reduced, the cleaning sheet can be used without waste.

According to a fifth aspect of the present invention, in the image forming apparatus of the fourth aspect, the transport distance is a value obtained by subtracting a distance that the cleaning sheet moves downstream in the transport direction by the cleaning operation from a distance between the contact portions. Is also a short distance.
According to this configuration, the image carrier can be reliably cleaned by the unused portion of the cleaning sheet.

According to a sixth aspect of the present invention, in the image forming apparatus according to the fourth or fifth aspect, the control unit performs the conveyance operation and the cleaning operation, and the cleaning sheet is provided adjacent to each other from the initial cleaning operation position. The process is repeated a plurality of times until the distance between the contact portions of the two image carriers and the cleaning sheet is conveyed.
According to this configuration, the cleaning sheet can be used more efficiently.

  A seventh invention is the image forming apparatus according to the third invention, wherein the most upstream image carrier is a monochrome image carrier carrying a monochrome developer, and the image forming apparatus is When the leading end portion of the cleaning sheet is transported to at least a position facing the monochrome image carrier, the cleaning unit further includes a monochrome cleaning mode in which the cleaning operation is started. And switch to the monochrome cleaning mode.

  According to this configuration, since the cleaning of the color image carrier is unnecessary, the cleaning operation can be started when the leading edge of the cleaning sheet is conveyed to the position facing the monochrome image carrier. The cleaning operation can be started immediately after switching to the cleaning mode.

  According to an eighth aspect of the present invention, there is provided an image carrier cleaning method comprising: an image carrier that carries a developer; and a conveying unit that conveys a sheet to the image carrier, while sandwiching the sheet by rotational driving. A conveying unit including a nipping / conveying unit capable of conveying; an image forming mode for transferring the developer image on the image carrier onto the sheet; and a cleaning mode for removing deposits on the image carrier by a cleaning sheet. In the image forming apparatus, the cleaning method of the image carrier, wherein in the cleaning mode, the conveying means reaches at least the front end portion of the cleaning sheet to a position facing the image carrier. After the first conveying step and after the first conveying step, the driving of the conveying means is stopped and the holding conveying means A cleaning step for driving the image carrier in a state where the cleaning sheet is sandwiched, and after the cleaning step, the conveying means and the image carrier are driven to move the image carrier by a predetermined distance. A second conveying step of conveying the cleaning sheet; and a re-cleaning step of performing the cleaning step again after the second conveying step.

  According to the present invention, the cleaning operation in which the image carrier is cleaned by the cleaning sheet is performed a plurality of times at different locations on the cleaning sheet in a state where the cleaning sheet is held by the holding and conveying means. Therefore, the image carrier can be efficiently cleaned using the cleaning sheet effectively.

1 is a side sectional view showing a schematic configuration of a printer of the present invention. Block diagram schematically showing the electrical configuration of the printer The figure explaining conveyance of a cleaning sheet Diagram showing the relationship between photosensitive drum interval and transport distance Flow chart showing the flow of the cleaning process The figure which illustrates the cleaning operation state corresponding to the flow of cleaning processing

Next, an embodiment of the present invention will be described with reference to FIGS.
1. Overall Configuration of Printer FIG. 1 is a side sectional view showing a schematic configuration of a printer 1 as an example of an image forming apparatus of the present invention. The printer 1 is a direct tandem color LED printer that forms a color image using toners of four colors (black K, yellow Y, magenta M, and cyan C). In the following description, the left side in FIG. Moreover, in FIG. 1, the code | symbol is abbreviate | omitted suitably about the component same between each color. The image forming apparatus is not limited to a direct tandem color LED printer, and may be, for example, a color laser printer, a monochrome laser printer, or a complex machine having a copy function.

  The printer 1 includes a main body casing 2 and a paper feed tray 4 on the bottom of the main body casing 2 on which a plurality of sheets 3 (an example of sheets) can be stacked. A paper feed roller (an example of a conveying unit) 5 is provided above the front end of the paper feed tray 4, and the paper 3 stacked at the top in the paper feed tray 4 as the paper feed roller 5 rotates is the main casing 2. It is sent out to the supply path P1 provided in the front part.

  The supply path P1 is provided with an auxiliary paper feeding roller (an example of a conveying unit) 17 and a registration roller (an example of a nipping / conveying unit and an conveying unit) 6 having a driving roller 6A and a driven roller 6B. The drive roller 6A of the registration roller 6 is connected to the paper feed motor 47 through, for example, a gear mechanism (not shown), and the driving force of the paper feed motor 47 is transmitted to the drive roller 6A.

  Further, a manual feed guide 7 that can be tilted forward is provided on the front surface in the main body casing 2, and a manual feed opening 8 through which a user can insert the paper 3 is opened. The manual feed port 8 communicates with the registration roller 6 through a manual feed path P2, and a conveyance path P3 that communicates with the belt unit 13 of the image forming unit 12 is formed behind the registration roller 6.

  The registration roller 6 can transport the paper 3 sent from the supply path P1 or the paper 3 sent from the manual feed path P2 onto the belt unit 13 of the image forming unit 12 via the transport path P3. . A pre-registration sensor 9, a manual feed sensor 10, and a post-registration sensor 11 are provided on the supply path P1, the manual feed path P2, and the transport path P3, respectively. Each sensor 9, 10, and 11 detects the presence or absence of the sheet 3 at each position.

The image forming unit 12 includes a belt unit 13, an exposure unit 18, a process unit 20, a fixing unit 31, and the like.
The belt unit (an example of a conveying unit) 13 includes an annular belt 15 that is stretched between a pair of front and rear belt support rollers 14. As the belt support roller 14 on the rear side is driven to rotate, the belt 15 circulates in the clockwise direction in the figure, and the paper 3 carried on the upper surface of the belt 15 is conveyed backward. In addition, four transfer rollers 16 are provided inside the belt 15.

  Above the belt unit 13, four exposure units 18 and a process unit 20 are provided. Each exposure unit 18 includes an LED unit corresponding to each color of black, yellow, magenta, and cyan, and each exposure unit 18 has an LED head 19 at the lower end thereof. Each exposure unit 18 is controlled to emit light based on image data to be formed, and irradiates light from the LED head 19 to the surface of the photosensitive drum 28.

  The process unit 20 includes four process cartridges 20K, 20Y, 20M, and 20C corresponding to the four colors. Each of the process cartridges 20K to 20C includes a cartridge frame 21 and a developing cartridge 22 that is detachably attached to the cartridge frame 21. Each developing cartridge 22 includes a toner storage chamber 23 that stores toner of each color as a developer, and includes a supply roller 24, a developing roller 25, a layer thickness regulating blade 26, and the like below.

  The toner discharged from the toner storage chamber 23 is supplied to the developing roller 25 by the rotation of the supply roller 24, and is positively frictionally charged between the supply roller 24 and the developing roller 25. Further, as the developing roller 25 rotates, the toner supplied onto the developing roller 25 enters between the layer thickness regulating blade 26 and the developing roller 25, where it is further sufficiently frictionally charged to have a constant thickness. It is carried on the developing roller 25 as a thin layer.

  A photosensitive drum (an example of an image carrier) 28 whose surface is covered with a positively chargeable photosensitive layer and a charger 29 are provided below the cartridge frame 21. The photosensitive drum 28 forms a nip portion with the corresponding transfer roller 16 via the belt 15. During image formation, the surface of the photosensitive drum 28 is uniformly positively charged by the charger 29. Then, the positively charged portion is exposed by the exposure unit 18 and an electrostatic latent image is formed on the surface of the photosensitive drum 28.

  Next, the positively charged toner carried on the developing roller 25 is supplied to the electrostatic latent image on the surface of the photosensitive drum 28, whereby the electrostatic latent image on the photosensitive drum 28 is visualized. Thereafter, the toner image carried on the surface of each photosensitive drum 28 has a negative polarity applied to the transfer roller 16 while the sheet 3 passes through each nip position between the photosensitive drum 28 and the transfer roller 16. The images are sequentially transferred onto the paper 3 by the transfer voltage.

  The sheet 3 on which the toner image has been transferred is then conveyed to the fixing device 31 by the belt unit 13. The fixing unit 31 includes a heating roller 31A having a heat source and a pressure roller 31B that presses the sheet 3 toward the heating roller 31A. While the sheet 3 passes through the fixing device 31, the image forming surface side of the sheet 3 is pressed against the heating roller 31A, and the transferred toner image is heat-fixed on the sheet surface. The sheet 3 thermally fixed by the fixing device 31 is conveyed upward and discharged onto the upper surface of the main casing 2 by the discharge roller 33.

  The printer 1 includes an image forming mode in which the toner image on the photosensitive drum 28 is transferred onto the paper 3 and a cleaning mode in which the deposits on the photosensitive drum 28 are removed by the cleaning sheet 50. In the cleaning mode, a cleaning sheet 50 is supplied from the paper feed tray 4 or the manual feed port 8 instead of the paper 3. For example, when the cleaning sheet 50 is placed on the paper supply tray 4 and supplied to the paper supply tray 4, the cleaning sheet 50 includes the paper supply roller 5 and the cleaning sheet 50 as shown in FIG. It is conveyed to the position of each photosensitive drum 28 by conveying means such as the auxiliary paper feeding roller 17. Then, deposits on the respective photosensitive drums 28 are removed by the cleaning sheet 50.

2. Electrical Configuration FIG. 2 is a block diagram schematically showing the electrical configuration of the printer 1.

  As shown in FIG. 1, the printer 1 includes a CPU 40 (an example of a control unit and a switching unit), a ROM 41, a RAM 42, and an NVRAM (nonvolatile memory) 43. Connected to these are an image forming unit 12, a pre-registration sensor 9, a manual feed sensor 10, a post-registration sensor 11, a display unit 45, an operation unit 46, a paper feed motor 47, and the like.

  The display unit 45 includes a liquid crystal display, a lamp, and the like, and displays various setting screens and operation states of the apparatus. The operation unit 46 includes a plurality of buttons, and various input operations are performed by the user.

  The ROM 41 stores various programs for executing operations of the printer 1 such as a cleaning process to be described later. The CPU 40 stores the processing results in the RAM 42 or the NVRAM 43 according to the programs read from the ROM 41. Take control.

  For example, the CPU 40 switches between the image forming mode and the cleaning mode in accordance with an instruction from the operation unit 46 by the user. When the image forming mode is selected, the CPU 40 controls the image forming unit 12 to transfer the toner image on the photosensitive drum 28 onto the paper 3 and form an image on the paper 3.

  On the other hand, when the cleaning mode is selected, a cleaning operation of the photosensitive drum 28 is executed. As shown in FIG. 3, in the cleaning operation, the CPU 40 controls at least the photosensitive drum 28 at the front end portion (near the most advanced portion) 50 </ b> A of the cleaning sheet 50 by controlling the conveying means such as the belt unit 13 and the registration roller 6. When the sheet is conveyed to the position opposite to, the driving of the conveying means is stopped. Then, the CPU 40 rotates the photosensitive drum 28 in a state where the cleaning sheet 50 is sandwiched by the sandwiching and conveying means such as the registration roller 6.

  Here, the position of the front end portion 50A of the cleaning sheet 50 is detected by, for example, the elapsed time from the time when the front end portion 50A is detected by the post-registration sensor 11. That is, since the conveyance speed of the cleaning sheet 50 by the conveyance unit and the distance from the post-registration sensor 11 to the paper nip portion of the photosensitive drum 28 are known, the CPU 40 determines the elapsed time from the detection time of the post-registration sensor 11. The position of the tip portion 50A can be recognized.

  After this initial cleaning operation, the CPU 40 drives the conveying means and the photosensitive drum 28, and the rear end of the cleaning sheet 50 from the portion 50 </ b> F held by the registration roller (nipping and conveying means) 6 during the cleaning operation of the cleaning sheet 50. A transport operation for transporting the cleaning sheet 50 by a predetermined distance (corresponding to “predetermined distance”: transport distance during cleaning) Lm shorter than the distance to the portion 50B (hereinafter referred to as “cleaning sheet remaining length”) Lr is executed, and again, The cleaning operation is performed. Here, the upper limit is set for the conveyance distance during cleaning (hereinafter simply referred to as “conveyance distance”) Lm. If the conveyance distance Lm is equal to or longer than the remaining cleaning sheet length Lr, the cleaning sheet 50 is not held between the registration rollers 6. . Therefore, the cleaning operation for driving the photosensitive drum 28 in a state where the cleaning sheet 50 is sandwiched between the registration rollers 6 cannot be performed again on the same photosensitive drum 28.

  Thus, in this embodiment, when the photosensitive drum 28 is cleaned using the cleaning sheet 50, the cleaning operation is performed a plurality of times by changing the location of the cleaning sheet 50 used for cleaning.

  Note that the conveyance distance (corresponding to the predetermined distance and the conveyance distance in the present invention) Lm is the distance between the contact portions of the two adjacent photosensitive drums 28 and the cleaning sheet 50 (equal to the photosensitive drum interval; see FIG. 3). ) It is preferable to set the distance not to be an integral multiple of Ld. At that time, when the leading end portion 50A of the cleaning sheet 50 is transported to the position facing the photosensitive drum 28C that is the most downstream in the transport direction, the CPU 40 transports the photosensitive drums 28K, 28Y, 28M, and 28C after performing the cleaning operation. The conveyance operation is executed for the distance Lm, and the cleaning operation for each photosensitive drum is executed again. In this case, when the cleaning operation is performed again, it is possible to avoid cleaning the other photosensitive drum (image carrier) 28 at the cleaned portion, and the cleaning can be performed efficiently.

  Further, in this embodiment, as shown in FIG. 3, the registration roller 6 is used as the nipping and conveying means during the cleaning operation. However, the present invention is not limited to this. For example, the auxiliary paper feeding roller 17 is nipped and conveyed during the cleaning operation. It may be a means.

3. Cleaning Processing Operation Next, the cleaning processing operation in the present embodiment will be described in detail with reference to FIGS. FIG. 4 is a diagram showing the relationship between the photosensitive drum interval Ld and the cleaning conveyance distance Lm. FIG. 5 is a flowchart showing the flow of the cleaning processing operation, and FIG. 6 is a diagram showing the cleaning operation state corresponding to the flow of the cleaning processing.

Here, an example is shown in which, when the cleaning mode is selected, the cleaning operation is performed, for example, four times on each color photosensitive drum 28. In this case, the conveyance distance (conveyance distance during cleaning) Lm is, as shown in FIG.
Lm = (Ld / n) −Lc = (Ld / 4) −Lc
It becomes. Here, Lc corresponds to the distance that the cleaning sheet 50 moves downstream in the conveyance direction by one cleaning operation, that is, the amount of displacement of the cleaning sheet 50 during the cleaning operation. This “displacement” is caused by the rotation of the photosensitive drum 28 during the cleaning operation, because the cleaning sheet 50 is not completely fixed by the registration rollers (nipping and conveying means) 6. In other words, it can be said that the shifted portion Lc of the cleaning sheet 50 substantially corresponds to the cleaning use portion of the cleaning sheet 50. In this way, by considering the deviation Lc with respect to the transport distance Lm, it is possible to avoid cleaning the other photosensitive drum (image carrier) 28 at the cleaned portion, and it is possible to efficiently clean.

  Thus, the transport distance Lm in this embodiment satisfies the upper limit condition (Lm <Lr). The conveyance distance Lm is a distance shorter than the distance (photosensitive drum interval) Ld between the contact portions between the two photosensitive drums (image carrier) adjacent to each other and the cleaning sheet 50, and is an integer of the photosensitive drum interval Ld. Not twice. Furthermore, since (Ld / 4) −Lc <Ld−Lc, the transport distance Lm is shorter than the value obtained by subtracting the deviation Lc during the cleaning operation from the photosensitive drum interval Ld. Therefore, the amount of movement of the cleaning sheet 50 when performing the cleaning operation again can be reduced, and the cleaning sheet 50 can be used without waste. Further, a cleaning sheet 50 having a short length can be used.

  In the present embodiment, the photosensitive drum interval Ld between the photosensitive drums 28 is assumed to be equal. The photosensitive drums 28 are simultaneously driven in synchronization.

  Now, for example, when the cleaning mode is selected by the user via the operation unit 46, the CPU 40 starts the cleaning process according to a predetermined program. As shown in FIG. 5, the CPU 40 first clears the number of cleaning operations in one cleaning process in step S100. Next, in step S105 (corresponding to a “first conveyance process”), the CPU 40 starts a conveyance of the cleaning sheet 50 to the cleaning start position, a belt motor (not shown), a sheet feeding motor 47, and a photosensitive element. Turn on the drum motor (not shown). Then, the paper feed roller 5, the registration roller 6, the belt support roller 14, the photosensitive drum 28, and the heating roller 31A start rotating, and the conveyance of the cleaning sheet 50 from the paper feed tray 4 is started.

  In the following, including step S105, it is optional to rotate the heating roller 31A when the cleaning sheet 50 is conveyed. However, it is preferable to rotate the fixing unit 31 so that the cleaning sheet 50 is not jammed by the fixing unit 31 when the cleaning sheet 50 is conveyed. At this time, there is no need to heat the heating roller 31A.

  Next, in step S110, the CPU 40 determines whether or not the leading end portion 50A of the cleaning sheet 50 has reached the fourth color, that is, the cyan C transfer position (nip position). If the leading end portion 50A has not reached the cyan C transfer position (S110: NO), the conveyance of the cleaning sheet 50 is continued until the leading end portion 50A reaches the cyan C transfer position. On the other hand, if it is determined that the tip portion 50A has reached the cyan C transfer position (corresponding to “conveyance 1” in FIG. 6), the process proceeds to step S115.

  In step S115, the CPU 40 starts cleaning each photosensitive drum 28. That is, the rotation of the photosensitive drum motor and the heating roller motor is continued, and the belt motor and the paper feed motor 47 are turned off (corresponding to “cleaning step”: corresponding to “cleaning 1” in FIG. 6). In this case, the photosensitive drum 28 is rotated while the cleaning sheet 50 is sandwiched between the registration rollers 6, and the photosensitive drum 28 is cleaned by the cleaning sheet 50 while the cleaning sheet 50 is displaced by the rotation of the photosensitive drum 28.

  Next, in step S120, the CPU 40 determines whether or not the cleaning time has passed the predetermined time “a” seconds. When the cleaning time has reached the predetermined time “a” seconds (S120: YES), in step S125, the belt motor and the paper feed motor are turned on in order to convey the cleaning sheet 50 by the conveyance distance Lm, that is, the photosensitive drum. The rotation of the motor and the heating roller motor is continued, and the rotation of the belt motor and the paper feed motor is started (corresponding to “second transport step”: corresponding to “transport 2” in FIG. 6). Then, the number of cleanings is incremented (S130), and it is determined whether or not the number of cleanings is 4 or more (S135). The predetermined time “a” seconds is, for example, a time required for at least one rotation of the photosensitive drum 28.

  When the number of times of cleaning is less than 4 (S135: NO), in step S140, the CPU 40 determines whether or not the minute conveyance time has passed the predetermined time “b” seconds. The predetermined time “b” seconds corresponds to a time during which the cleaning sheet 50 is conveyed by the conveyance distance Lm. Here, the conveyance distance Lm is recognized by multiplying the conveyance speed (known amount) of the cleaning sheet 50 by the conveyance time.

  When the predetermined amount of time “b” seconds has elapsed (S140: YES), that is, when the cleaning sheet 50 has been conveyed by the conveyance distance Lm, the process returns to step S115 to start the second cleaning (“ Corresponding to “re-cleaning step”): corresponding to “cleaning 2” in FIG. The processing from step S115 to step S140 is repeated until the fourth cleaning is completed (corresponding to “cleaning 4” in FIG. 6).

  When the fourth cleaning is completed (S135: YES), in step S145, the CPU 40 performs the discharging process of the cleaning sheet 50 while continuing the rotation of each motor, and the cleaning sheet 50 is discharged onto the upper surface of the main body casing 2. .

  Here, the cleaning process in which the cleaning operation is performed four times within one photosensitive drum interval Ld may be repeated a plurality of times without discharging the cleaning sheet 50. That is, after the previous cleaning operation, the cleaning sheet 50 may be conveyed by a distance of 3 Ld (+ α), and the process of performing the current cleaning operation on the unused portion of the cleaning sheet 50 may be repeated. In this case, the cleaning effect is further improved by increasing the number of times of cleaning. In order to repeat the above cleaning process, in which the cleaning operation is performed four times within one photosensitive drum interval Ld, a plurality of times so as not to be cleaned at the already cleaned portion, the length of the cleaning sheet 50 is at least as long as possible. A length of (6Ld + the distance from 50F to 50C in FIG. 3) is required.

  When the cleaning sheet 50 is discharged and the conveyance of the cleaning sheet is completed, the CPU 40 turns off the belt motor, the paper feed motor, the photosensitive drum motor, and the like in step S150 and ends the cleaning processing operation.

  As described above, in the present embodiment, the CPU 40 performs the conveying operation and the cleaning operation of the cleaning sheet 50 with the two image carriers and the cleaning sheet 50 that are adjacent to each other from the initial cleaning operation position. This is repeated a plurality of times until the distance (photosensitive drum interval) Ld between the contact portions is conveyed.

  The number of cleaning operations “n” at the photosensitive drum interval Ld is arbitrary. Further, when the cleaning process performed four times is repeatedly performed a plurality of times, one cleaning operation may be performed for each photosensitive drum interval Ld. In this case, the transport distance Lm is Ld <Lm <Lr, and the use length and cleaning time of the cleaning sheet 50 in one cleaning operation can be made longer than in this embodiment, and the number of cleaning operations is four times at the photosensitive drum interval Ld. Since it is reduced compared with the case where it is performed, the number of steps during the cleaning process can be reduced. In this embodiment, the cleaning sheet 50 is supplied from the paper feed tray. However, the cleaning sheet 50 may be supplied from the manual feed port 8.

4). Effects of the Present Embodiment As described above, according to the present embodiment, the photosensitive drums 28K, 28Y, 28M, and 28C (image bearing members) in a state where the cleaning sheet 50 is sandwiched by the registration rollers 6 (the sandwiching and conveying unit). The cleaning operation in which the cleaning sheet 50 is cleaned is performed a plurality of times at different locations on the cleaning sheet 50. Therefore, each photosensitive drum 28 can be efficiently cleaned using the cleaning sheet 50 effectively.

Particularly, since the cleaning operation by the cleaning sheet 50 is performed a plurality of times (four times) within the movement distance of the photosensitive drum interval Ld, the movement amount of the cleaning sheet 50 when performing the cleaning operation again can be reduced, and the cleaning sheet 50 can be removed. It can be used without waste, and each photosensitive drum 28 can be effectively cleaned.
Further, since cleaning is started in a state where the front end portion 50A of the cleaning sheet 50 is conveyed to the position (nip position) facing the photosensitive drum 28C which is the most downstream in the conveying direction, the photosensitive drum 28, the belt 15 (conveying means), and the like. Wear due to direct rubbing can be suppressed.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In the above embodiment, when the printer (image forming apparatus) 1 has a plurality of photosensitive drums 28 (image carriers), the cleaning operation is performed on the photosensitive drums 28K, 28Y, 28M, and 28C. However, the present invention is not limited to this. For example, when the front end portion 50A of the cleaning sheet 50 is conveyed to at least a position facing the most upstream photosensitive drum to be cleaned in the conveyance direction among the plurality of photosensitive drums 28, the CPU 40 detects the most upstream photosensitive drum. After that, the cleaning operation may be performed for the transport distance Lm, and the cleaning operation for the most upstream photosensitive drum may be performed again.

  Usually, there is a high probability that deposits on the photosensitive drum other than the developer, such as paper dust, adhere to the most upstream image photosensitive drum. Therefore, in this configuration, it is possible to efficiently remove deposits on the photosensitive drum by cleaning only the most upstream photosensitive drum without cleaning all the photosensitive drums. Further, since only the most upstream photosensitive drum needs to be cleaned, the cleaning sheet can be shortened.

  In the case of this configuration, if the most upstream photosensitive drum (image carrier) and the other photosensitive drums can be driven separately, only the most upstream image carrier is driven during the cleaning operation. By stopping the driving of the other image carrier, it is possible to reliably suppress wear caused by direct friction between the image carrier and the conveying means, which is more preferable. That is, the front end portion 50A of the cleaning sheet 50 is in a state in which the image carrier and the conveying means are in direct contact with each other in a state where the front end portion 50A is not conveyed to the position facing the photosensitive drum 28C (image carrier) downstream in the conveyance direction. In addition, wear due to direct rubbing between the image carrier and the conveying unit is reliably suppressed.

  Further, as in the present embodiment, the most upstream photosensitive drum (image carrier) is a monochrome photosensitive drum 28K carrying a monochrome developer. When the leading end portion 50A of the cleaning sheet 50 is conveyed to at least a position facing the monochrome photosensitive drum 28K by the conveying unit, the printer 1 (image forming apparatus) performs a monochrome cleaning mode in which a cleaning operation is started. You may make it provide further. At that time, it is preferable that the CPU (switching means) 40 switches to the monochrome cleaning mode when the frequency of color image formation is low.

According to this configuration, the cleaning operation is started when the leading end 50A of the cleaning sheet 50 is transported to the position facing the monochrome image carrier using the fact that the color image carrier need not be cleaned. Therefore, the cleaning operation can be started immediately after switching to the cleaning mode. In this configuration, when the frequency of color image formation is not low, for example, as in the above-described embodiment, the normal cleaning mode in which the cleaning operation for each photosensitive drum 28 is performed may be switched.
(2) In the above embodiment, an example is shown in which the photosensitive drum interval Ld is equal. However, the present invention can also be applied to image forming apparatuses having different photosensitive drum intervals Ld.
(3) In the above embodiment, the photosensitive drums 28 are driven simultaneously in synchronism. However, the present invention can also be applied to an image forming apparatus in which the photosensitive drums 28 can be individually driven.
(4) In the above-described embodiment, an example in which the present invention is applied to the printer (image forming apparatus) 1 provided with a plurality of photosensitive drums (image carriers) to carry the developer of each color has been described. The present invention can also be applied to an image forming apparatus having a single image carrier.

DESCRIPTION OF SYMBOLS 1 ... Printer 3 ... Paper 6 ... Registration roller 11 ... Post-registration sensor 12 ... Image forming part 13 ... Belt unit 28 ... Photosensitive drum 40 ... CPU
50 ... Cleaning sheet 50A ... Front end portion 50B of cleaning sheet ... Rear end portion of cleaning sheet

Claims (8)

An image carrier carrying a developer;
A conveying unit that conveys the sheet to the image carrier, the conveying unit including a nipping / conveying unit that can convey the sheet while nipping the sheet by rotation driving;
Switching means for switching between an image forming mode for transferring the developer image on the image carrier onto the sheet and a cleaning mode for removing deposits on the image carrier by a cleaning sheet;
In the cleaning mode, when the leading end portion of the cleaning sheet is conveyed to at least a position facing the image carrier by the conveying unit, the driving of the conveying unit is stopped and the cleaning conveyance unit performs the cleaning operation. A cleaning operation for driving the image carrier in a state where the sheet is sandwiched is performed, and thereafter, a transport operation for transporting the cleaning sheet by a predetermined distance is performed by driving the transport unit and the image carrier. Control means for performing the cleaning operation again;
An image forming apparatus comprising: The image forming apparatus according to claim 1.
A plurality of the image carriers are provided to carry the developer of each color,
The conveying means is opposed to each image carrier and conveys the sheet to each image carrier.
The predetermined distance is a conveyance distance that does not become an integral multiple of the distance between the contact portions between the two image carriers adjacent to each other and the cleaning sheet,
When the leading end portion of the cleaning sheet is transported to a position facing the image carrier at the most downstream side in the transport direction, the control unit performs the transport by the transport distance after the cleaning operation is performed on the image carriers. An image forming apparatus that executes an operation and again executes the cleaning operation for each of the image carriers. The image forming apparatus according to claim 1.
A plurality of the image carriers are provided to carry the developer of each color,
The conveying means is opposed to each image carrier and conveys the sheet to each image carrier.
The predetermined distance is a conveyance distance that is not an integral multiple of the distance between the contact portions between two image carriers adjacent to each other and the cleaning sheet,
When the front end portion of the cleaning sheet is conveyed to at least a position facing the most upstream image carrier to be cleaned in the conveyance direction of the plurality of image carriers, the control unit An image forming apparatus that performs the cleaning operation on the image carrier, thereafter performs the transport operation for the transport distance, and again executes the cleaning operation on the most upstream image carrier. The image forming apparatus according to claim 2 or 3,
The image forming apparatus, wherein the transport distance is shorter than a distance between contact portions between two image carriers adjacent to each other and the cleaning sheet. The image forming apparatus according to claim 4.
The image forming apparatus, wherein the conveyance distance is a distance shorter than a value obtained by subtracting a distance by which the cleaning sheet moves downstream in the conveyance direction by the cleaning operation from a distance between the contact portions. The image forming apparatus according to claim 4 or 5, wherein:
The control unit performs the transport operation and the cleaning operation by transporting the cleaning sheet by a distance between the contact portions between the two image carriers adjacent to each other and the cleaning sheet from the initial cleaning operation position. An image forming apparatus that repeats a plurality of times before being performed. The image forming apparatus according to claim 3.
The most upstream image carrier is a monochrome image carrier carrying a monochrome developer,
The image forming apparatus includes:
A monochrome cleaning mode for starting the cleaning operation when at least a front end portion of the cleaning sheet is transported to the position facing the monochrome image carrier by the transport unit;
The image forming apparatus that switches to the monochrome cleaning mode when the color image formation is small. An image carrier that carries the developer, a conveyance unit that conveys the sheet to the image carrier, and includes a conveyance unit that can convey the sheet while nipping the sheet by rotation driving; A method for cleaning the image carrier in an image forming apparatus comprising: an image forming mode for transferring the developer image on the sheet; and a cleaning mode for removing deposits on the image carrier with a cleaning sheet. There,
In the cleaning mode,
A first conveying step of conveying the leading end portion of the cleaning sheet by the conveying means until at least a position facing the image carrier is reached;
A cleaning step of stopping the driving of the conveying unit after the first conveying step and performing a cleaning operation for driving the image carrier in a state where the cleaning sheet is held by the holding and conveying unit;
After the cleaning step, a second conveying step of driving the conveying means and the image carrier and conveying the cleaning sheet by a predetermined distance;
A re-cleaning step of performing the cleaning step again after the second transport step;
A method for cleaning an image carrier comprising:

Images